The transfer mold encapsulation process has been used with thermoset molding compounds, such as epoxy molding compounds, for about 30 years. Conventional transfer molds used in this process are typically high density molds with as few as 20 cavities to over 800 cavities per molded encapsulation shot. Both multi-plunger and single plunger systems are used.
The entrapment of air in mold compound introduces voids in the molded semiconductor package, producing defective devices, or devices that cannot pass inspection due to voids in the package surface.